VATICAN CITY (CNS) -- Black smoke poured from the Sistine Chapel chimney on the conclave's opening evening, signaling that the cardinals had failed to elect a pope on their first ballot.

Thousands of people who had gathered in St. Peter's Square April 18 went away disappointed, but hardly surprised. Few expected a candidate to immediately obtain the two-thirds majority needed for election.

A first wisp of light-colored smoke raised expectations in the crowd, but it was soon followed by thick clouds of dark smoke.

The 115 cardinals were to return the next day for four more ballots, and continue -- with occasional pauses for reflection -- until they had chosen the 265th pope.

The cardinals opened the conclave with a public Mass. Later in the day the cardinal-electors, dressed in brilliant red vestments, processed into the Sistine Chapel behind a tall gilded crucifix, chanting a litany of saints.

After passing slowly through the frescoed halls leading to the chapel, they took their seats and settled in to elect Pope John Paul II's successor.

It was the final act in a drama marked by liturgical pageantry, private contemplation and consensus-building among the cardinals entrusted with choosing the next pope.

The conclave was the largest in history. It was also the most geographically representative, with cardinals from 52 countries.

Eleven U.S. cardinals -- including Cardinal William W. Baum, who used a walker for support in the procession -- entered the conclave. Cardinal Baum was one of only two cardinal-electors who had participated in a conclave before.

The faces of the cardinal-electors betrayed little emotion as they filed from the Hall of the Blessings, through the Sala Regia and into the historic chapel, dominated at one end by Michelangelo's fresco of the "Last Judgment."

In a corner at the opposite end stood the small stove where ballots would be burned, signaling to the waiting world whether a new pope had been elected.

Led by Cardinal Joseph Ratzinger, dean of the College of Cardinals, they recited an oath to follow the rules of the conclave and maintain absolute secrecy about its proceedings.

They also promised that "whichever of us by divine disposition is elected Roman pontiff will commit himself faithfully to carrying out the 'munus Petrinum' (Petrine ministry) of pastor of the universal church."

Each cardinal then came to the center of the hall, placed his hand on an open Book of the Gospels, and swore to uphold the oath.

With the words Extra omnes ("Everyone out"), all but two nonelectors were ordered to leave the chapel and the doors were closed. Then Cardinal Tomas Spidlik, a Jesuit too old to vote in the conclave, delivered a talk to the cardinals on the grave duty they faced and the need to act for the good of the whole church.

Finally, only the voting cardinals were left inside and the first vote was taken. Each cardinal marked his ballot in secret, folding it twice and depositing it in a silver and bronze urn. After the ballots were counted, they were burned with special chemicals to produce the black smoke signifying an inconclusive vote.

Earlier in the day, the cardinals and the faithful gathered for a Mass in St. Peter's Basilica and prayed for the election of a man marked by "holiness of life" and a spirit of service.

The 78-year-old Cardinal Ratzinger, one of the most frequently mentioned candidates, presided over the Mass and delivered a stern warning about a "dictatorship of relativism" in modern society and "ideological currents" that have rocked the church in recent decades.

"The small boat of thought of many Christians has often been tossed about by these waves -- thrown from one extreme to the other: from Marxism to liberalism, even to libertinism; from collectivism to radical individualism; from atheism to a vague religious mysticism; from agnosticism to syncretism," he said.

"Every day new sects are created and what St. Paul says about human trickery comes true, with cunning which tries to draw people into error," he said.

Cardinal Ratzinger, who headed the Vatican's doctrinal congregation under the late pope, said having a true faith today is often labeled "fundamentalism."

The cardinal did not mention the papal election until the last line of his homily. He prayed that, after Pope John Paul, God would again give the church "a pastor according to his own heart, a pastor who guides us to knowledge in Christ, to his love and true joy."

The liturgical prayers and readings made frequent reference to the need to choose a good pastor.

"O God, eternal Father, you who govern your people with the care of a father, give your church a pontiff pleasing to you for his holiness of life, totally consecrated to the service of your people," said the opening prayer.

The cardinals had been meeting daily for two weeks to discuss church issues and to begin considering potential candidates for the papacy. Despite an official news blackout by the cardinals, leaks and rumors fueled speculation about a wide array of "papabili."

U.S. Catholics at the Mass had their own ideas about the papal election.

"I'd like to see a Latin American. The church has so many followers there," said Ivonne Fleitas, a Cuban-American Catholic from Miami.

Gennaro Cibelli, a Catholic from Clarksville, Md., said it was important to choose someone with a "sturdy character."

"He doesn't have to be a carbon copy of John Paul, but someone with the same moral fortitude," he said.

To ensure total secrecy, Vatican technicians swept the Sistine Chapel area for electronic surveillance or recording devices. The Vatican said the chapel would be jammed to disable cell phone signals.

At least for the first phase of the conclave, a two-thirds majority -- 77 votes out of 115 -- was needed to elect a pope. The cardinals could move to a simple majority after about 12 days, but few observers expected the voting to go on that long.

After the first day, the cardinals were scheduled to vote twice in the morning and twice in the evening. The balloting continues until a new pope is chosen, with a day off for prayer after every three days of voting.

Only cardinals under the age of 80 could vote, which meant that 66 elderly cardinals would be waiting on the outside for the results. Two under-80 cardinals -- Philippine Cardinal Jaime Sin of Manila and Mexican Cardinal Adolfo Suarez Rivera, retired archbishop of Monterrey -- were too sick to make the trip to Rome.

As the world waited, media attention was focused on the Sistine Chapel chimney. Ballots were to be burned twice a day, morning and evening, with white smoke signaling the election of a pope.

Because of past confusion about the smoke, organizers of this conclave connected a separate electric stove and ventilator to the cylindrical cast-iron stove, which has been used since 1939. The electric unit was designed to burn chemical packets, enhancing the color of the smoke, and preheat the copper smokestack to improve the draw.

Lest there be any doubt, organizers said the ringing of bells would also signal a successful election.

The first conclave of the third millennium was marked by a number of other innovations.

The cardinals were no longer sequestered in the rooms surrounding the Sistine Chapel, but were being housed in a Vatican residence hall, the Domus Sanctae Marthae, a quarter-mile away.

The cardinals could either take a shuttle bus to the Sistine or walk the same route, along the street behind St. Peter's Basilica. The Vatican said the cardinals' path would be temporarily cleared of others working in the Vatican.

During the conclave, cardinals were to have no contact with the outside world, including newspapers, radio and TV. The staff of their residence hall, medical assistants and even the cardinals' bus driver had to take an oath swearing to protect the cardinals' privacy and the conclave's secrecy.

The cardinals were to begin each day with a 7:30 a.m. Mass in the chapel of their residence, where they were also taking their meals. By 9 a.m. they were to be inside the Sistine Chapel, reciting the Liturgy of the Hours before voting.

The two rounds of morning balloting were expected to conclude by noon, and the cardinals were to return to the residence. At 4 p.m., they were due back in the Sistine Chapel for two more rounds of voting, ending by 7 p.m.

The Vatican said St. Peter's Basilica would continue to be open during the conclave. This included Pope John Paul's tomb in the grotto area, where thousands of pilgrims were visiting.

The dome of St. Peter's, which overlooks the Sistine Chapel, was closed for the duration of the conclave. Also closed were the Vatican Gardens, where the cardinals were free to stroll -- as long as they asked permission beforehand and were accompanied.

On April 16, the cardinals held the last of their "general congregations," daily meetings to discuss the challenges faced by the church and the practical affairs of the papal transition period.

Vatican spokesman Joaquin Navarro-Valls said the meetings were marked by a family atmosphere and a "great consensus" on the main themes. As for the papal election, he said, "they never talked about names" during the meetings.

The news media, instead, was full of names. Most of the speculation reflected the fact that there was no dominant candidate when the pope died.

Italian media reported a groundswell of support for Cardinal Ratzinger midway through the general congregations, but said later that his candidacy appeared destined to fall short of the needed 77 votes. Cardinals who spoke to Catholic News Service downplayed the predictions, saying the discussions were general and that no one was tallying votes before the conclave began.

Cardinal Cormac Murphy-O'Connor of Westminster said April 17 that the cardinals' talks during the general congregations had been "fruitful and prayerful." He said he had been moved by the intervention of an African cardinal who had spoken of the challenges of "aggressive Islam, AIDS, poverty and wars."

Celebrating Masses in Rome the same day, several other cardinals declined to talk about the contents of their meetings, but emphasized that the pope had not yet been chosen.